[fitswcs] FITS WCS Time Paper

[patrick.wallace at stfc.ac.uk]

Arnold,


> And that is precisely what is meant, although in many cases
> it will also coincide with the spacetime origin

OK, understood.  Perhaps it would be clearer to omit "An
observation is an event in space-time", which is a bit too general
to add much, and then to say:

 "The reference position, specified by the keyword TREFPOS, specifies
  the spatial location at which the time is valid, either where the
  observation was made or the point in space for which light time
  corrections have been applied."

> So, yes, we mean "wrt Earth".

Fair enough.  I was evaluating the sentence out of context, and had
not spotted that it had been introduced with "At this point we
recommend synchronizing the local clock with one of the time scales
defined on the Earth’s surface".  I was thinking of what would
happen if you set a spacecraft clock to TDB.


Patrick Wallace
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Space Science & Technology Department                +44-1235-531198
STFC Rutherford Appleton Laboratory
Harwell Oxford
Didcot, Oxfordshire, OX11 0QX, UK         Patrick.Wallace at stfc.ac.uk
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